Not familiar with the H15, but I don't believe any furler system can work without a swivel at the top. Where are you located? The H15 is a Euro product, no? Perhaps a dealer over there could help? Here's some further info for reference, but I'm not sure about fitment issues...
Pages 27 and 28 of the Parts Guide from Hobie France (
https://media.hobie.com/digital_assets/hc16_part_guide_202207.pdf?_gl=1*8s7pnr*_ga*MTY4NDE2MDc3MC4xNjg0MjMxNTU3*_ga_Z9H2YY9GHV*MTY5NDA4MjA1NC4zOC4xLjE2OTQwODMyNjMuNDkuMC4w) show furling system parts for the Hobie 16, including the swivel (H Euro Part No. 18060590) on Page 27.
My (US) H14 Turbo is rigged as in the document kinked by dorienc, except there is no 10-hole adjuster at the top. The swivel is swaged onto the upper forestay/pigtail (your "extra short bit") as shown in the pic at the upper right of Page 2 of that document. Apparently that part (H US Part No. 10810010) is currently out of stock from Hobie US (
https://westcoastsailing.net/hobie-14-forestay-upper-turbo/). Here's one at Murray's (
https://www.murrays.com/product/02-0134-0/). And Salty Dog has one available on their Ebay store (
https://www.ebay.com/itm/141934348023?hash=item210bf246f7:g:hv4AAOSwHxVW7Xj6).
Hope this helps some.